Reproduction in a South American mouse, Abrothrix longipilis

Abstract

Approximately 700 Abrothrix longipilis were trapped in Argentina, and their reproductive organs were studied. Some were kept briefly in captivity. Males have the same body length as females but are 8% heavier. Sexually immature males are shorter and lighter than breeding males of the same age. Few individuals in the wild live as long as two years. All overwintering males come into breeding condition in the spring and become infertile in the autumn. All overwintering females have open vaginas in the spring, and most undergo several infertile ovulatory cycles, probably without copulating, before they become pregnant. Corpora lutea of the sterile cycles accumulate; there may be as many as 28 in a pair of ovaries. The average number of ova shed per cycle is 4.66; average litter size is 3.85. Ovulation is spontaneous. There is postpartum ovulation and fertilization without intervening sterile cycles but with maintenance of old corpora lutea. Unusual architecture of the penis and vagina may result from unusual timing of hormone production during development, and the disjunction of ovulation and fertilization may similarly result from hormonal heterochrony at the beginning of the breeding season. The apparently nonadaptive wastage of ova in sterile cycles may be a novel example of kin selection.

Population dynamics of five sigmodontine rodents of northwestern Patagonia

“…The sexual maturation delay in summer cohorts as was observed during this study, has also been described for other rodent species (eg Gonzalez andMurua 1985, Zuleta et al 1988). A. longipilis individuals became sexually mature a year after they were born as described by Pearson (1992).…”

Testing models of diversification in mice in the Abrothrix olivaceus/xanthorhinus complex in Chile and Argentina

“…The existence of a central and southern Andean clade composed of the genera Abrothrix , Chroeomys , Chelemys , Geoxus , Notiomys and Pearsonomys is strongly supported by mitochondrial DNA (mtDNA) sequences (Smith & Patton 1993, 1999) as well as by karyotypic and reproductive characteristics (Spotorno 1986; Spotorno et al . 1990; Pearson 1992). These taxa are well‐differentiated from the genus Akodon , where many of them were placed previously (Thomas 1916; Gyldenstolpe 1932; Tate 1932; Musser & Carleton 1993).…”

Morfologia dos órgãos genitais masculinos de pacas (Agouti paca Linnaeus, 1766)

“…As glândulas genitais acessórias que observamos na paca foram as mesmas encontradas na cobaia (HILLYER e QUESENGERRY, 1997), já no rato, alem destas, foram encontradas as glândulas ampolares, localizadas na dilatação do ducto deferente (JUNQUEIRA e MARTINS, 1947;GRIFFITH e FARRIS, 1942e Chiasson, 1969; no rato branco as glândulas ampolares caracterizavam-se por pequenos nódulos que cercavam o ducto deferente na sua chegada, na uretra. Pearson (1992) no Abrothríx, Hansen (2001) , 1948), já no rato topeira, Gotteich et al (1996), afirmaram que esta espécie parecia não apresentar as glândulas vesiculares e coaguladoras. Neuhaus et al (2001) observaram muitas glândulas genitais acessórias no trato urinário baixo da cobaia, porém esses autores descreveram apenas a presença da próstata e das glândulas coaguladoras para esses animais.…”

“…Também em nossas observações encontramos, em continuação ao corpo cavernoso do pênis na paca, uma estrutura óssea em posição dorsal à glande; tal constatação assemelha-se mais às descrições de Griffith e Farris (1942), ao relatarem que o pênis do rato mostrava um único processo cartilaginoso ou ósseo, o osso peniano. Também para Hansen (2001), em muitos carnívoros, roedores, primatas não humanos e morcegos o corpo cavernoso aparece parcialmente ossificado (osso peniano ou baculum); esse osso peniano também foi observado por Pearson (1992) em quase todos os roedores Cricetidios Sul Americanos e no Abrothix longipilis.…”